The German specification 1,204,731 refers to a current conductor arrangement which has grooves or recesses, in each of which a metallic tape with a small cross section is placed. The contacts with the electrical appliances, which are attached to the current conductor rod, are with the metallic tapes in the groove of the current conductor rod for the transmission of current in the electrical contact. Axial displacement of the appliance contacts on the current conductor rail is admittedly possible, but it is not possible to twist the electrical appliance on the outer periphery of the current conductor rod, since the electrical contact of the appliance is set in the groove or grooves with the metallic tape and thus the current conductor there. Furthermore, owing to the small cross section of the metallic tape the known arrangement is only suitable for low amperages.
The German examined specification 3,120,267 describes a current conductor arrangement having rail parts between which an insulating member is placed. This insulating member has two rib which project past the peripheral line of the rail parts. In this known current conductor arrangement the two ribs are absolutely necessary. If they were absent, there would be short circuiting on twisting the contact element by which the lamp fixed to the contact element is supplied with current. A further function of the rib-like insulating intermediate layer projecting past the peripheral limit of the circular portions is that of providing a switching and switching off function. The ribs needed for preventing a short circuit do however have the disadvantage that the contact parts, with which the lamps are attached to the rail and via which the electrical conduction takes place between the lamp and the current rail, is not able to be evenly turned over the entire periphery of the current conducting rail without the projecting ribs impairing both the mechanical strength of the press fit and also the electrical contact between the lamp and the current conductor. The contact surfaces of the lamps are not positioned by the ribs provided on the current conductor in relation to said current conductor rod and the contact is only provided over a small area of the contact interfaces so that the contact conductor cross section is small. The same also applies for the suggestion made in the said reference about the cross section of the current conductor being polygonal and adapted to the circular cross section form. Even in the case of such a design of the current conductor the contact area between the contact interface of the lamp and the rail part is limited to the edges of the polygon. Apart from the fact that this impairs the mechanical strength of the contact connection by the small area between the lamp contact and the current conductor and with a reduction in friction, the contact transition cross section between the lamp contact and the outer face of the current conductor is small so that there will be small transition cross sections and thus high current densities which on twisting of the contact element lead to sparking and arcing.